* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
ul {
  list-style: none;
}
#app {
  width: 100vw;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}
#app .cover {
  box-shadow: 0 0 5px #666;
  width: 400px;
  padding: 20px;
}
#app .cover h1 {
  text-align: center;
  height: 60px;
  line-height: 60px;
  cursor: pointer;
}
#app .cover ul {
  height: 0px;
  overflow: hidden;
  transition: all 0.5s;
}
#app .cover ul li {
  height: 40px;
  line-height: 40px;
}
.active {
  height: 120px !important;
}
.v-enter-from,
.v-leave-to {
  height: 0px;
}
.v-enter-active,
.v-leave-active {
  height: 100%;
  transition: all 1s;
}
.v-enter-to,
.v-leave-from {
  height: 100%;
}
